How Forests Make Seafood

PHYTOPLANKTON ARE TOO small to be seen with the naked eye, yet they are vital to all life on the planet. They are abundant in the world’s oceans and, through their process of photosynthesis, they are tasked with the job of turning sunlight into food for other sea-dwelling creatures. Experiments have proven that their numbers are greatly enhanced when iron is added to the ocean. The importance of iron led one path-breaking scientist to make a unique connection. The Erimo Peninsula on the north coast of Japan saw its forests clear-cut and its hills turned into pasture long ago. The change drove off the schools of fish that once teemed there, and caused a decline in oyster populations. Katsuhiko Matsunaga, a Japanese marine chemist, spent years studying the relationship between forests and oceans.

His key finding is that even where iron is abundant in parts of the ocean, it is oxygenated, which means it is not readily available for the tiny creatures. What can make iron available to phytoplankton to perform photosynthesis, however, is fulvic acid, one of several humic acids that comes from the decay of leaves and other organic matter. The ongoing, natural decomposition of centuries of tree leaves and other material on the forest floor, and the leaking, leaching, and washing of this chemical stew into the ocean, is vital to increasing coastal phytoplankton, and thus the things that eat them, and those that eat them, from oysters all the way to whales. The award-winning chemist spent much of his life working with fishermen in coastal communities to reforest the coast and the banks of rivers and streams to increase fish stocks, and he wrote about it, in Japanese, in one of his papers, “When Forests Disappear the Sea Dies.”

- Excerpted from the book, The Man Who Planted Trees: A Story of Lost Groves, the Science of Trees, and a Plan to Save the Planet by Jim Robbins.